A deep dissatisfaction with the status quo. (Ability to see things not just as they are, but as they might be). This is what drives you. The people who build incredible companies under them don't do it just because they like the idea of being successful. They do it because they absolutely can't bear the idea of NOT creating and stewarding something that matters to them.

Love for tinkering, experimenting. You need to always be creating. We're looking for persistence, a willingness to fail, and a willingness to try new things.

Willingness to tolerate volatility and unpredictability. You will have to manage your own health, well-being, etc, but you won't really get to operate on a fixed schedule. Some people just aren't cut out for this.

Ability to prioritize and focus on the most important thing. Much easier said than done--the most important thing is usually messy, ugly, painful, unglamorous.

Willingness to sacrifice. This can sometimes include personal relationships, familarity, comfort zones. You may need to fire people. You'll be seen as the bad guy (or gal). You have to bear that.

Knack + taste for debugging systems--especially your own head. You need to know what you're wrong about, and how to systematically, consistently improve your odds. How do you reduce your margin of error? How do you reduce your odds of error? How do you protect against downside?

A feel for numbers. You don't necessarily need complicated math skills, but you need to be able to at least handle your budget. And you need to understand compound interest. And rate of change. Play some video games.

People skills. Entrepreneurs are problem-solvers. If you're going to solve big problems, you're going to have to work with people. You might not necessarily get along with everybody, you might not necessarily be the most loved person around, but you need to be able to motivate people, to challenge and inspire them.

Appetite for learning. I think this might be the most important one of all, because it influences almost everything else. A common trait among entrepreneurs? They read a lot. They talk to smarter people. They never stop learning. As Jobs would say, creativity is just connecting things. The more you know, in a thoughtful, self-directed way, the more opportunities you see.